Allergic sensitisations during the life course. Results of the KiGGS cohort

Background Allergic sensitisations of the immune system involve the formation of specific immunoglobulin E (IgE) antibodies after (initial) contact with certain otherwise harmless sub­ stances (allergens). Repeated contact with allergens, how­ ever, sensitises the immune system. On subsequent con­ tact, the immune system recognises these allergens and this triggers a reaction by its defence mechanisms. Allergic reactions can affect different organs, have different degrees of severity and show various symptoms. Although allergic sensitisations are measurable by analysing the levels of IgE antibodies in the blood, detecting these antibodies does not provide a measurement of disease, rather they are mere­ ly associated with an increased risk of allergic diseases [1]. There are four different types of allergic reaction. Type I hypersensitivity, also referred to as the immediate type, is the most common form and it is mediated by IgE antibod­ ies. Some of the best known manifestations of Type I aller­ gies include hay fever and (allergic) asthma. These condi­ tions are among the most common chronic diseases in childhood and adolescence, they place significant burdens on health and have strong socioeconomic consequences [2, 3]. An important aspect of epidemiological allergy research is the extent to which sensitisations persist and how they may develop or even decline during the life course. In particular, this applies to sensitisations to important inhalant allergens that play a significant role in the devel­ opment of hay fever and asthma. Only limited data are available that can be used to calculate transition probabil­ ities. However, as part of the KiGGS cohort – the largest cohort for children and adolescents in Germany – mea­ surements were taken of important specific IgE antibodies that are associated with the most commonly occurring allergic diseases. These measurements were made during the KiGGS baseline study (2003­2006) and KiGGS Wave 2 (2014­2017). This data can help answer the important ques­ tion about the extent to which allergic sensitisations per­ sist, arise or even decline over a period of more than ten years. This article, therefore, uses the longitudinal data from the KiGGS cohort to investigate the transition prob­ abilities of allergic sensitisations during the transition from childhood to young adulthood.


Background
Allergic sensitisations of the immune system involve the formation of specific immunoglobulin E (IgE) antibodies after (initial) contact with certain otherwise harmless sub stances (allergens).Repeated contact with allergens, how ever, sensitises the immune system.On subsequent con tact, the immune system recognises these allergens and this triggers a reaction by its defence mechanisms.Allergic reactions can affect different organs, have different degrees of severity and show various symptoms.Although allergic sensitisations are measurable by analysing the levels of IgE antibodies in the blood, detecting these antibodies does not provide a measurement of disease, rather they are mere ly associated with an increased risk of allergic diseases [1].
There are four different types of allergic reaction.Type I hypersensitivity, also referred to as the immediate type, is the most common form and it is mediated by IgE antibod ies.Some of the best known manifestations of Type I aller gies include hay fever and (allergic) asthma.These condi tions are among the most common chronic diseases in childhood and adolescence, they place significant burdens on health and have strong socioeconomic consequences [2,3].An important aspect of epidemiological allergy research is the extent to which sensitisations persist and how they may develop or even decline during the life course.
In particular, this applies to sensitisations to important inhalant allergens that play a significant role in the devel opment of hay fever and asthma.Only limited data are available that can be used to calculate transition probabil ities.However, as part of the KiGGS cohort -the largest cohort for children and adolescents in Germany -mea surements were taken of important specific IgE antibodies that are associated with the most commonly occurring allergic diseases.These measurements were made during the KiGGS baseline study (20032006) and KiGGS Wave 2 (20142017).This data can help answer the important ques tion about the extent to which allergic sensitisations per sist, arise or even decline over a period of more than ten years.This article, therefore, uses the longitudinal data from the KiGGS cohort to investigate the transition prob abilities of allergic sensitisations during the transition from childhood to young adulthood.

Indicator and methodology
The analyses are based on measurements made of specific IgE antibodies that react against the allergen mixture SX1, a mixture of eight common inhalant allergens (timothy, rye grass, birch, mugwort, cat and dog dander, house dust mite and the fungus Cladosporium herbarum -Phadia, now Thermo Scientific, Freiburg).Measurements were made from 2,041 girls and 2,143 boys who participated in the cohort study and who were examined both during the base line study (20032006) and during KiGGS Wave 2 (2014 2017).The participants were aged 3 years or older at the time of the first measurement.Transition probabilities were calculated as the percentage probability of a transition from nonsensitisation to sensitisation to the allergen mixture SX1 or vice versa during the period beginning with the KiGGS baseline study and ending with KiGGS Wave 2. The value of ≥0.35 kU/l was used to set the limit of positive sensitisations.A possible bias due to selective reparticipa tion was partially offset by multivariate weighting [4,5].

Sample size: 15,023 participants KiGGS cohort study in KiGGS Wave 2 Age range: 10 31 years Sampling:
Reinvitation of everyone who took part in the KiGGS baseline study and who was willing to participate in a followup Sample size: 10,853 participants

Sensitisation to an allergen mixture of eight common inhalant allergens (SX1 test) over a 10-year period of the life course
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